I was having similar problems when I switched to 6K before putting my car away for winter. I ordered a relatively cheap set on Ebay to try out 6K and it was doing all kinds of weird things....not coming on, one side would come on, come on and if I turned the car on then off, lights would not come on...frustrating...especially getting to the bulb is annoying if leaving the wheels on.
I will probably buy a more expensive set, seems the 6K was really needed after painting my headlights though...my lights looked more dull with the dark housing, 6K is amazing!
I'll check out JWMotoring then